diff --git a/package.json b/package.json
index 84a4183..8971b79 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@authsignal/browser",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "type": "module",
   "main": "dist/index.js",
   "module": "dist/index.js",
diff --git a/src/authsignal.ts b/src/authsignal.ts
index 73a0364..c5a2662 100644
--- a/src/authsignal.ts
+++ b/src/authsignal.ts
@@ -32,6 +32,10 @@ export class Authsignal {
     this.cookieDomain = cookieDomain || getCookieDomain();
     this.anonymousIdCookieName = cookieName;
 
+    if (!tenantId) {
+      throw new Error("tenantId is required");
+    }
+
     this.passkey = new Passkey({tenantId, baseUrl});
 
     const idCookie = getCookie(this.anonymousIdCookieName);